out of memory

[matthiaskrgr]

Unfortunately there is no kind of error or warning given by rustc, it just OOMs right away :/

I tried this code:

trait Default {
    type Id;

    fn intu(&self) -> &Self::Id;
}

impl<T: Default<Id = U>, U: Copy> Default for U {
    default type Id = T;
    fn intu(&self) -> &Self::Id {
        self
    }
}

fn specialization<T>(t: T) -> U {
    *t.intu()
}

use std::num::NonZero;

fn main() {
    let assert_eq = NonZero::<u8, Option<NonZero<u8>>>(0);
    assert_eq!(specialization, None);
}

I expected to see this happen: explanation

Instead, this happened: explanation

Meta

rustc --version --verbose:

rustc 1.80.0-nightly (faefc618c 2024-05-07)
binary: rustc
commit-hash: faefc618cf48bd794cbc808448df1bf3f59f36af
commit-date: 2024-05-07
host: x86_64-unknown-linux-gnu
release: 1.80.0-nightly
LLVM version: 18.1.4

[matthiaskrgr]

#0  0x00007ffff1775d80 in ?? () from /usr/lib/libc.so.6
#1  0x00007ffff5062575 in <hashbrown::raw::RawTable<(rustc_query_system::query::job::QueryJobId, rustc_query_system::query::job::QueryJobInfo)>>::reserve_rehash::<hashbrown::map::make_hasher<rustc_query_system::query::job::QueryJobId, rustc_query_system::query::job::QueryJobInfo, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>::{closure#0}> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#2  0x00007ffff50b5fb6 in <hashbrown::map::HashMap<rustc_query_system::query::job::QueryJobId, rustc_query_system::query::job::QueryJobInfo, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>::insert ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#3  0x00007ffff506d555 in <rustc_query_system::query::plumbing::QueryState<()>>::try_collect_active_jobs::<rustc_middle::ty::context::TyCtxt> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#4  0x00007ffff51355fa in rustc_query_impl::query_impl::early_lint_checks::try_collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#5  0x00007ffff5129c7c in <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#6  0x00007ffff50815e1 in rustc_query_system::query::plumbing::cycle_error::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#7  0x00007ffff5c8981b in rustc_query_impl::query_impl::def_span::get_query_non_incr::__rust_end_short_backtrace () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#8  0x00007ffff5fccac6 in rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#9  0x00007ffff512b943 in rustc_query_impl::plumbing::create_query_frame::<rustc_span::def_id::LocalDefId> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#10 0x00007ffff511851b in <rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#11 0x00007ffff506b7da in <rustc_query_system::query::plumbing::QueryState<rustc_span::def_id::LocalDefId>>::try_collect_active_jobs::<rustc_middle::ty::context::TyCtxt> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#12 0x00007ffff5135c1a in rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#13 0x00007ffff5129c7c in <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#14 0x00007ffff50815e1 in rustc_query_system::query::plumbing::cycle_error::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#15 0x00007ffff5c8981b in rustc_query_impl::query_impl::def_span::get_query_non_incr::__rust_end_short_backtrace () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#16 0x00007ffff5fccac6 in rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#17 0x00007ffff512b943 in rustc_query_impl::plumbing::create_query_frame::<rustc_span::def_id::LocalDefId> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#18 0x00007ffff511851b in <rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#19 0x00007ffff506b7da in <rustc_query_system::query::plumbing::QueryState<rustc_span::def_id::LocalDefId>>::try_collect_active_jobs::<rustc_middle::ty::context::TyCtxt> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#20 0x00007ffff5135c1a in rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#21 0x00007ffff5129c7c in <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#22 0x00007ffff50815e1 in rustc_query_system::query::plumbing::cycle_error::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#23 0x00007ffff5c8981b in rustc_query_impl::query_impl::def_span::get_query_non_incr::__rust_end_short_backtrace () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#24 0x00007ffff5fccac6 in rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#25 0x00007ffff512b943 in rustc_query_impl::plumbing::create_query_frame::<rustc_span::def_id::LocalDefId> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#26 0x00007ffff511851b in <rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#27 0x00007ffff506b7da in <rustc_query_system::query::plumbing::QueryState<rustc_span::def_id::LocalDefId>>::try_collect_active_jobs::<rustc_middle::ty::context::TyCtxt> () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#28 0x00007ffff5135c1a in rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#29 0x00007ffff5129c7c in <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::collect_active_jobs () from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
#30 0x00007ffff50815e1 in rustc_query_system::query::plumbing::cycle_error::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> ()
   from /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/librustc_driver-baba34ae40c356f7.so
```

[matthiaskrgr]

This gave an error back in 1.76 but in 1.77 it started just OOM without giving any output.

1.76:

error[E0432]: unresolved import `std::num::NonZero`
  --> oom.rs:18:5
   |
18 | use std::num::NonZero;
   |     ^^^^^^^^^^-------
   |     |         |
   |     |         help: a similar name exists in the module: `NonZeroI8`
   |     no `NonZero` in `num`

error[E0412]: cannot find type `U` in this scope
  --> oom.rs:14:31
   |
14 | fn specialization<T>(t: T) -> U {
   |                   -           ^
   |                   |
   |                   similarly named type parameter `T` defined here
   |
help: a type parameter with a similar name exists
   |
14 | fn specialization<T>(t: T) -> T {
   |                               ~
help: you might be missing a type parameter
   |
14 | fn specialization<T, U>(t: T) -> U {
   |                    +++

error[E0658]: specialization is unstable
 --> oom.rs:8:5
  |
8 |     default type Id = T;
  |     ^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information

error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
 --> oom.rs:7:6
  |
7 | impl<T: Default<Id = U>, U: Copy> Default for U {
  |      ^ unconstrained type parameter

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0207, E0412, E0432, E0658.
For more information about an error, try `rustc --explain E0207`.

[cuviper]

Infinite recursion from cycle_error? Here's a more detailed backtrace from a debug build:

...
#24 0x00007ffff2a9e841 in rustc_query_system::query::plumbing::cycle_error<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> () at compiler/rustc_query_system/src/query/plumbing.rs:253
#25 0x00007ffff48a3cbc in rustc_query_system::query::plumbing::try_execute_query<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> () at compiler/rustc_query_system/src/query/plumbing.rs:370
#26 0x00007ffff456fa34 in rustc_query_system::query::plumbing::get_query_non_incr::{closure#0}<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> () at compiler/rustc_query_system/src/query/plumbing.rs:801
#27 stacker::maybe_grow<rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::query::plumbing::get_query_non_incr::{closure_env#0}<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt>> ()
    at /home/jistone/.cargo/registry/src/index.crates.io-6f17d22bba15001f/stacker-0.1.15/src/lib.rs:55
#28 rustc_data_structures::stack::ensure_sufficient_stack<rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::query::plumbing::get_query_non_incr::{closure_env#0}<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt>> ()
    at compiler/rustc_data_structures/src/stack.rs:17
#29 rustc_query_system::query::plumbing::get_query_non_incr<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> ()
    at compiler/rustc_query_system/src/query/plumbing.rs:801
#30 rustc_query_impl::query_impl::def_span::get_query_non_incr::__rust_end_short_backtrace ()
    at compiler/rustc_query_impl/src/plumbing.rs:596
#31 0x00007ffff5d70913 in rustc_middle::query::plumbing::query_get_at<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>> () at compiler/rustc_middle/src/query/plumbing.rs:145
#32 0x00007ffff47fb932 in rustc_query_impl::plumbing::create_query_frame<rustc_span::def_id::LocalDefId> ()
    at compiler/rustc_query_impl/src/plumbing.rs:333
#33 0x00007ffff47497ac in rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs::{closure#0} ()
    at compiler/rustc_query_impl/src/plumbing.rs:699
#34 core::ops::function::FnOnce::call_once<rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs::{closure_env#0}, (rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)> ()
    at library/core/src/ops/function.rs:250
#35 0x00007ffff4874fd4 in rustc_query_system::query::plumbing::QueryState::try_collect_active_jobs<rustc_span::def_id::LocalDefId, rustc_middle::ty::context::TyCtxt> () at compiler/rustc_query_system/src/query/plumbing.rs:89
#36 0x00007ffff474a00d in rustc_query_impl::query_impl::local_def_id_to_hir_id::try_collect_active_jobs ()
    at compiler/rustc_query_impl/src/plumbing.rs:701
#37 0x00007ffff46c2b46 in rustc_query_impl::plumbing::{impl#3}::collect_active_jobs ()
    at compiler/rustc_query_impl/src/plumbing.rs:85
#38 0x00007ffff2a9e841 in rustc_query_system::query::plumbing::cycle_error<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> () at compiler/rustc_query_system/src/query/plumbing.rs:253
...

Since stacker::maybe_grow is in there, it can recurse until OOM.

[apiraino]

Bisection points to fb4bca0 (but unsure if directly related) cc @reitermarkus @dtolnay

bisected with cargo-bisect-rustc v0.6.8

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --without-cargo --preserve --start 1.76.0 --end 1.77.0 --timeout 2 --script test.sh 

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-medium

[cuviper]

This frame is suspicious, since the code around it is already trying to avoid infinite recursion:

#32 0x00007ffff47fb932 in rustc_query_impl::plumbing::create_query_frame<rustc_span::def_id::LocalDefId> ()
    at compiler/rustc_query_impl/src/plumbing.rs:333

rust/compiler/rustc_query_impl/src/plumbing.rs

Lines 328 to 334 in cf77474

	let span = if kind == dep_graph::dep_kinds::def_span || reduce_queries {
	// The `def_span` query is used to calculate `default_span`,
	// so exit to avoid infinite recursion.
	None
	} else {
	Some(key.default_span(tcx))
	};

cc @Zoxc who added that reduce_queries check.

I think maybe it should set the reduced state here, e.g. this seems to work:

diff --git a/compiler/rustc_query_impl/src/plumbing.rs b/compiler/rustc_query_impl/src/plumbing.rs
index a7696b1fbaff..7a9a1fafc579 100644
--- a/compiler/rustc_query_impl/src/plumbing.rs
+++ b/compiler/rustc_query_impl/src/plumbing.rs
@@ -330,7 +330,7 @@ pub(crate) fn create_query_frame<
         // so exit to avoid infinite recursion.
         None
     } else {
-        Some(key.default_span(tcx))
+        Some(ty::print::with_reduced_queries!(key.default_span(tcx)))
     };
     let def_id = key.key_as_def_id();
     let def_kind = if kind == dep_graph::dep_kinds::def_kind || reduce_queries {